Mail server settings issue

Hello all,

I am having an issue with getting my mail server settings to work correctly. The odd thing is they were working from about 12 hours then suddenly stopped. I am getting the error below.

FAILURE :Email Settings saved successfully. But error occurred while trying to check connection with mail server - Authentication Failed:[Logon failure: unknown user name or bad password.]

the username for the account is correct as is the password as I am able to log in to the mailbox without issue. The mailbox is on Office 365 and I am wondering if there is some sort of security to block "unknown" connections to it. Has anyone seen or heard of this? I am a long time user of SDP but my experience is solely with the in house setup with my own Exchange and AD servers. Unfortunately in my present position we have Exchange in the cloud and I have minimal access to AD.

Thanks in advance for any assistance you can provide.

Chris